l. Field of the Invention
This invention relates to a recording apparatus, and more specifically to a recording apparatus which can change resolution.
2. Related Background Art
FIG. 8 is a block diagram of a known printing apparatus. In the apparatus shown in FIG. 8, a host device 40 sends print data, etc., to a controller 50, which performs data processing on the print data sent from the host device 40 and outputs the processed data to a printer engine 60. The function of the printer engine 60 is to print out the print data received from the controller 50 with a designated format and resolution.
The controller 50 includes an input unit 51 for receiving the data from the host device 40, an interpretation/storage unit 52 for separating control commands from print data by analyzing the data sent from the host device 40 through the input unit 51, and a page buffer memory 53 for storing the print data. The controller 50 also includes a pattern information storage unit 54 for storing a printing pattern, such as a character pattern, corresponding to the print data, and a development control unit 55 for performing pattern development of the printing pattern from the pattern information storage unit 54 or of image pattern data from the page buffer memory 53 to a frame memory 56, which is also part of the controller 50. The controller 50 further includes an output control unit 57 for outputting image pattern data from the page buffer memory 53 or image data from the frame memory 56 to a printer engine control unit 61 in the printer engine 60.
In the known printing apparatus, data sent from the host device 40 is received by the input unit 51, and the interpretation/storage unit 52 analyzes whether the received data belongs to the category of control commands, or of print data. The print data is processed in a known fashion, and the processed print data is stored in the page buffer memory 53. The development control unit 55 reads out the print data stored in the page buffer memory 53 for conversion into a corresponding printing pattern by the pattern information storage unit 54, and development of the printing pattern in the frame memory 56.
Meanwhile, the page buffer memory 53 stores both print data for one page and control information relating to printing circumstances. The output control unit 57 sends the image data stored in the frame memory 56 to the printer engine 60 in accordance with the control information, and controls the printer engine 60 to print the image data out on a recording sheet.
In the known printing apparatus, printing resolution of the printer engine 60 based on the control by the output control unit 57 is fixed, generally at several hundreds of dpi (dots per inch).
In a known dot impact printer, a high-resolution image can be printed out by decreasing the rate of movement of the recording head, when image data is printed. However, in such a known dot impact printer, if such compressed printing is performed, the quality of the printed image is affected by superimposing of dots, because the size of the dots is constant. And in the case where a character pattern is printed, instead of the above-described manner of printing, only a printing at the resolution peculiar to the printer in question is executed.
A known PDL (page description language) or a known DTP (desk top publishing) system can execute a complex print processing with a high quality and in fact can be made to produce a combined image of text information and graphic images on the same page. Even in this case, the same resolution is employed for printing out both text and graphic portions, resulting in the defect that the quality of the graphic images deteriorates, although the quality of the characters or text is good.
Accordingly, in the known system, the resolution of the printing device employed in the system is increased to solve the above-described defect; specifically, the quality of all the printing is raised to correspond to what is needed for the graphic images. However, in the case where a high-resolution character pattern is provided for printing with graphic images, a large-capacity storage is required for storing the character pattern. Or, in a case where the character pattern is generated internally, much time is required for producing the character pattern from stored character information because of the high resolution of the character pattern, as a result of which a lowering of throughput cannot be avoided.
Further, a large-capacity RAM is required as the frame memory because the whole area of the printing image consits of a high-resolution image, which increases the cost of the system.